Strong exciton–photon coupling in a low-Q all-metal mirror microcavity

Abstract

We report the experimental observation of strong exciton-photon coupling in a planar microcavity composed of an organic semiconductor positioned between two metallic ͑silver͒ mirrors. Via transmission and reflectivity measurements, we observe a very large, room temperature Rabi splitting in excess of 300 meV. We show that the Rabi-splitting is enhanced in all-metal microcavities by a factor of more than 2 compared to an organic film positioned between a silver mirror and a dielectric mirror. This enhancement results from the significantly larger optical fields that are confined within all-metal microcavities. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1517714͔Placing emitters of light such as excitons within microcavities is attractive for device applications and allows the study of new optical phenomena. The effect of the microcavity on the emission of light can be divided into two regimes. In the weak-coupling regime, the spatial and temporal distribution of the emitted radiation can be altered. This regime is employed in applications such as vertical cavity surface emitting lasers and resonant cavity light emitting diodes. 1,2In the strong-coupling regime, a mixing between optical and electronic ͑excitonic͒ states within the cavity occurs, leading to the appearance of new states termed cavity-polaritons. 3This effect is an intensive area of research due in part to the interest in coherent, stimulated effects in such systems that may lead to new optical devices. 4 The field has recently expanded to include Frenkel excitons supported by organic materials. [5][6][7] This has been important in that it has led to the observation of significantly larger, room temperature, strongcoupling effects, and opens the possibility of easily fabricated nonlinear optical devices.A key phenomenon associated with strong-coupling 8 is the anticrossing of the exciton and photon mode where, in the absence of a strong interaction, they would have crossed. Until now, investigations into strong-coupling in organic and inorganic materials have been conducted either using two Bragg reflectors ͑DBR͒ as microcavity mirrors or one Bragg reflector together with one optically thick metal mirror. In this letter we show that microcavities fabricated using just two metal mirrors can operate in the strong-coupling regime. All-metal cavities are characterized by relatively low Q-factors; 9 however we find that strong-coupling can still be achieved because the effective optical path length in an allmetal cavity is significantly shorter than that in microcavities based on one or more dielectric mirrors, providing a significant enhancement of the optical field within the organic semiconductor region of the cavity. Because of this enhancement we observe very large Rabi-splittings of over 300 meV.J-aggregates of organic dye molecules possess many features that make them particularly suitable to undergo strongcoupling in microcavities. 6 The narrow, inhomogeneous linewidths ͑40-50 meV͒ and very large oscillator strengths of molecular J-aggre...

Coupling of exciton-polaritons inlow−Qcoupled microcavities beyond the rotating wave approximation

“…5(a) for TM and (b) for TE polarization. The in-plane wave vector k is related to the incident angle θ and wavelength λ of the incident light through the relation k = sin θ(2π/λ) 14 . The measured anti-crossing dispersions as a function of the wave vector k also give the same Ω R value of 1.12 eV for both TM and TE polarization.…”

“…Organic semiconductor-based single microcavities composed by high-Q or low-Q reflectors, exhibiting large vacuum Rabi splitting, have been particularly interesting as strong and ultrastrong exciton-photon coupling can be readily attained at room temperature [12][13][14][15][16][17][18][19][20][21][22][23][24] . In this framework, due to the specific excitonic property of organic materials, allowing the ultrastrong coupling regime with a large Rabi splitting to be reached, the demonstration of such coupled multiple organic microcavities, each in the ultrastrong regime, suggests the potential for new physics and applications for tunable polariton-based devices operating at room temperature 25 , with new concepts in quantum information being one example 26 .…”

Exciton-phonon scattering and photoexcitation dynamics inJ-aggregate microcavities

“…Organic materials possess Frenkel excitons, instead of Wannier ones, with large binding energy and oscillator strength. Because of this, organic MCs allow obtaining values of the Rabi splitting up to 300 meV 5 and offer the possibility of easily observing polaritons at room temperature 6 . Electroluminescence was demonstrated in a J-aggregate strongly coupled microcavity LED 7 at room temperature.…”

Observation of strong exciton–photon coupling at temperatures up to 410 K

“…In these materials, the exciton binding energy is smaller than the thermal energy at RT and excitons are not stable at RT. Therefore, many efforts have been made to obtain microresonators with gain media that reveal an exciton binding energy larger than the thermal energy at RT, such as organic semiconductors [10,11], or GaN [7,12,13] and ZnO [14]- [16]. The advantage of organic semiconductors is their huge exciton oscillator strength resulting in a large coupling strength between the excitons and the cavity photons.…”